An extended Luenberger state observer is designed for solving the problems of system model uncertainties and exogenous perturbations. The lumped perturbation is reconstructed through a high-order Taylor polynomial as its internal model, and is treated as an extended state of the observer. A linear state feedback control method is employed to feed back the state estimates as the reference inputs. Then the stabilizing pole-placement method and the extended state estimate are combined to derive the final control action. The strong capability of disturbance rejection can be obtained through system linearization in the form of chain of integrations and effective disturbance compensation. Finally, numerical results show the effectiveness of the proposed method.